Diabetic Kidney Disease

Each kidney contains about a million filtering units, and each one is a tuft of very fine blood vessels with a delicate membrane that lets water and waste through while holding protein back. Years of high blood glucose damage that membrane and the vessels feeding it.

The damage follows a recognisable path. Early on the kidneys actually filter faster than normal, working under pressure. The membrane then begins to leak small amounts of albumin into the urine, and this is the earliest sign anybody can measure, appearing long before you feel anything. Over years the leak grows, scar tissue replaces working filters, and the filtration rate starts to fall.

Roughly one person in three with diabetes develops some degree of kidney damage, and how long you have had diabetes, how well the glucose has been controlled and how high your blood pressure runs are the main factors deciding whether you are one of them. High blood pressure and diabetes together do more harm than either alone. This is a slow process measured in years, and that is what makes it treatable.

Your nephrologist starts with the history: how many years since diabetes was diagnosed, what your sugar control has looked like over that time, what medicines you take, and whether anyone in your family has kidney disease.

The examination is aimed at the whole picture. Your blood pressure is measured carefully, sitting and standing, because the number guides the treatment more directly than almost anything else. Your ankles, shins and face are checked for fluid. Your feet are examined for sensation and circulation, and your eye records are asked for, since damage to the small vessels in the eye, the nerves and the kidney tends to run together, and finding one raises the suspicion of the others.

What your doctor is chiefly establishing is whether the picture fits diabetes or something else. Kidney damage that appears very suddenly, or in somebody whose eyes are entirely unaffected, or accompanied by blood in the urine, is investigated further, because assuming the diabetes is responsible would let a second, treatable cause go unnamed. Results are confirmed over three months before anything is concluded.

This is a condition that is controlled over years and is not cured, so the useful measure is not recovery but stability, and stability is realistic for most people.

Expect a review every three to six months, and more often at the start while medicines are being adjusted. When a new medicine is started, your kidney numbers and your potassium are rechecked within one to two weeks, and a small dip in the kidney figures at that point is expected and is usually a sign the drug is working as intended.

Give any change three to six months before judging it. The protein leak responds within weeks to months, and the rate at which filtration declines takes a year or more of readings to show a change. Bring your home blood pressure readings to every visit; they carry more weight than the single reading taken in the clinic.

Your own part is daily and unglamorous: the medicines taken exactly as prescribed, blood pressure down, glucose in range, salt cut hard, and no smoking. Avoid painkillers of the anti-inflammatory kind, which quietly do damage.